Tool heads capable of holding a blade are used in numerous minipulable implements intended for myriad applications in which the worker must, for example, cut into a workpiece or non-destructively scrape along a surface or substrate. One such application concerns wallpaper stripping tools manually operable for enabling separation and removal of a wall covering without inflicting damage on the underlying support surface.
A conventional wallpaper stripping tool, as heretofore known, is illustrated in FIGS. 1 and 2 and there identified by the general reference numeral 10. Tool 10 comprises a head 12 and a handle 14 elongated to impart a leveraged mechanical advantage in use of the tool and integrally fixed to or otherwise depending from the head. The major portion of the tool head is formed as a shell or body 16 to which handle 14 is secured at one of the body and which engages, at its opposite tapered end, an elongated blade 18 having a single honed cutting edge 20. More particularly, and as best seen in FIG. 2, the blade 18 is held between the tapered end of body 16 and a similarly tapered end of a cooperating clamping member 22 which is releasably secured to body 16 by a conventional threaded screw 24. Thus, by rotatably loosening screw 24 to loosen the securement of member 22 from body 16, blade 18 is freed from clamped engagement between the body and clamping member and may be removed and/or replaced; reverse rotation of the screw conversely effective to grip a new blade between the tapered ends. This arrangement also desirably enables positional reversal of the retained blade--so that its cutting edge 20 is then disposed protectedly between the tapered clamping ends of body 16 and member 22--during periods of storage or non-use of the tool to thereby prevent inadvertent injury to a worker or damage to nearby objects.
In use, the conventional tool 10 is held so as to apply the cutting edge of the blade to the wall to be stripped at a typical angle of approximately 10 to 30 degrees relative to the work surface. In order to facilitate removal of the wallpaper or other covering, the same is commonly first wet down or moistened with water. The tool handle is then manipulated to wedge the blade under the wall covering and move the blade along thereunder, separating the covering from the supporting wall surface. The illustrated taper of the blade holding edge faces of the tool head is necessary to prevent the head from scraping and damaging the wall as the tool-held blade is moved along its surface, for which reason the head of screw 24 is also generally recessed in body 16 as may be readily seen at 25 in FIG. 2.
This prior art arrangement for holding a blade in a tool head presents, however, a number of significant operating and structural drawbacks. The provision of a rotatable screw to retain the blade between the body and clamping member requires that a user of the tool have and use another tool--i.e. a screwdriver--with which to loosen and tighten the screw, and thereby release and secure the blade, in the tool head. The momentary unavailability of a screwdriver, or a user's disinclination to locate and/or use one, often leads a worker to leave the blade with its cutting edge outwardly exposed during brief--and even during extended--periods of non-use, dangerously presenting numerous opportunities for serious personal injury and property damage.
Wetting of the wall covering prior to scraping is known to facilitate separation of the covering from the wall surface by loosening or dissolving the glue bond existing therebetween. As the blade end of the tool head is then wedged and moved along between the covering and supporting wall surface, a gummy mixture of moistened glue and bits of shreaded wall covering material is forced along the tapered faces of the tool head, collecting in both the screw-receiving recess and the screw head spline. The screw thereby becomes difficult, at best, to rotate with a screwdriver, significantly interfering with the user's ability to tighten the blade-securing screw--as is necessary from time-to-time--and further discouraging reversing of the blade to sheath the cutting edge for safety during periods of non-use. Moreover, this caked mixture, wet or dry, can be extremely difficult to remove in cleaning the tool.
Yet another problem with the prior art wallpaper scraper construction 10 concerns the reliability of the screw-based arrangement for securely retaining the blade in the tool head. Tapering of the outer faces of body 16 and clamping member 22--which is necessary to lessen the possible infliction of damage to the wall surface being scraped--significantly reduces the thickness of the tool head through which retaining screw 24 is rotatably journaled. As a consequence, the length of the thread defined in clamping member 22 for engagement with the thread of screw 24 is relatively short; repeated tightening of the screw to maintain the blade securely held in the tool head often results in early stripping of the threads, thereby rendering the tool head useless for continued use. In an effort to overcome this deficiency, it is known to incorporate a boss 26, as seen in FIG. 2, projecting outward from the tapered face of clamping member 22 and located to provide additional length for the screw-receiving thread in member 22. Although the provision of such a boss does somewhat, although not entirely, alleviate the problem of early thread stripping, it raises the further difficulty of placing an upstanding projection on the otherwise smoothly tapered face of clamping member 22 which can easily, and often does, become caught on and destructively scrape the surface being stripped of its wall covering.
It is accordingly the desideratum of the present invention to provide a tool head capable of securely and releasably retaining a blade and incorporating an improved releasable retaining mechanism which overcomes the problems inherent in prior art devices.